Generation of ultralow power phononic combs

Abstract

We demonstrate excitation of phononic frequency combs in a Bulk Acoustic Wave system at a temperature of 20mK using a single tone low power signal source. The observed ultra low power threshold is due to a combination of very high quality factor of 4.2 × 10 8 and relatively strong nonlinear effects. The observed repetition rate of the comb varies from 0.7 to 2Hz and spans over tens of Hz. The demonstrated system is fully excited via piezoelectricity and does not require mode spectra engineering and external optical or microwave signals. It is shown that the comb profile significantly depends on geometry of excitation and detection electrodes. Observed strong Duffing nonlinearity below the generation threshold suggests that the system is a phononic analogue to Kerr frequency combs excited in monolithic optical microresonators. The ultra-low power regime opens a way of integrating this phononic system with quantum hybrid systems such as impurity defects and superconducting qubits.Photonic frequency combs generators are an important tool used for many scientific applications allowing to couple distant parts of frequency spectrum 1 . Amongst others, these important applications include ultra stable clocks and frequency metrology 2-4 and spectroscopy 5,6 . All of these system are photonic mostly utilising a carrier signal at an optical frequency and RF or microwave repetition rates. The most popular ways to generate such combs include mode-locked lasers 7 , (four)wave mixing/Kerr nonlinearity [8][9][10][11] . Despite the fact that phononic systems also play an important role in metrology and spectroscopy, demonstration of phononic or acoustic wave combs have been sporadic 12 . Moreover, their complexity, requirements to design a certain mode structure, very high threshold powers 13 and requirement for extra laser sources 14 make these systems inapplicable for many low energy applications. In these applications Bulk Acoustic Wave (BAW) devices found very extensive use, e.g. frequency metrology 15 , quantum hybrid systems 16-18 and fundamental physics tests [19][20][21][22] . Additionally both bulk and surface acoustic wave devices are utilised for spectroscopy 23 , detection and sensors [24][25][26] . Recently nonlinear dynamics of mechanical systems including comb generation has also became a subject of theoretical research 27 . All these areas could benefit from designing devices with frequency comb functionality.To excite frequency combs at low power levels, one needs a system with low losses and strong nonlinear effects. For these reasons, in this work, we employ a phonon trapping 28 SC-cut 29 quartz BAW cavity 30 operating at 20mK. The device is an SC-cut plano-convex shaped plate of 1mm thickness, 23mm diameter and 300mm the radius of curvature. Quartz BAW cavities have demonstrated extremely high values of Quality factors at cryogenic temperatures reaching the level of a) Electronic mail: maxim.goryachev@uwa.edu.au 8 × 10 919,30 . In the same time these devices are able to demonstrate a significant levels of non...

Acoustic frequency combs using gas bubble cluster oscillations in liquids: a proof of concept

“…Our current findings contribute to further development of an emergent field of AFC generation 11,[14][15][16][17] . They also extend our previous observation of frequency combs originating from the onset of Faraday waves in OPEN 1 Optical Sciences Centre, Swinburne University of Technology, Hawthorn, VIC 3122, Australia.…”

“…However, in that system the spacing between the peaks of the comb was only 20–40 Hz. Whereas frequency combs with a Hz-range spacing can find certain applications 17 , in the gas bubble system investigated in the present work we use the high-kHz range that can potentially be extended to the high-MHz range 24 . This opens up opportunities for using acoustic combs instead of optical ones or in addition to them in a number of practical situations where operation at higher frequencies may be required 16 .…”

“…Similar to optical frequency combs, acoustic (phononic) frequency combs (AFC)-purely acoustic signals with spectra containing equidistant coherent peaks-exploit the ability of acoustic waves to provide precision information about the medium in which they propagate [11][12][13][14][15][16][17] . In contrast to light, acoustic waves can propagate in water and opaque liquids over long distances, which underpins many acoustics-based technologies including sonar, underwater communication and sensing 15 and marine biology 18 .…”

Complex temperature dependence of coupling and dissipation of cavity magnon polaritons from millikelvin to room temperature

“…This is realized by a cavity resonator with two cylindrical posts in the cavity. Depending on the direction of current of each post, the field between the posts results in 'bright' and 'dark' modes [33]. In the 'bright' mode the post's magnetic fields interfere constructively and enhance the total magnetic field strength between the posts.…”

Hybrid integrated photonics using bulk acoustic resonators

“…The roll-off starting around 3.5 GHz is caused by reduced FSR due to coupling of the AlN cavity. This study of mechanical dispersion could benefit the growing field of mechanical dispersion engineering for future applications (e.g., mechanical dissipative solitons 40,41 , HBAR-based quantum random access memory 39,42 ) and future devices improvement by optimizing Si, SiO 2 , and AlN thicknesses or by choosing materials with different acoustic impedance. In this sense, further theoretical and numerical studies are necessary for a more complete understanding of the acoustic wave propagation and mechanical cavity coupling in such a platform.…”